The present invention pertains to an improved positive displacement pump of the type having a circular rotor eccentrically driven in a circular cylinder having a single vane extending therefrom. One disadvantage of such pumps is that they must be driven in a predetermined direction in order to obtain flow in a given direction through the pump. Although some may be driven in the opposite direction such operation results in a reversal of function of the pump inlet and outlet ports, unless relatively complicated and costly additional valving and/or other parts are provided. The present pump is particularly suited for use as an oil pump for lubricating a refrigeration compressor driven by a three-phase motor, because the start-up of such equipment can result in rotation in either direction.
The primary feature of the present invention resides in the provision of an improved design of this type of pump wherein the single vane automatically controls the flow of fluid through the pump to maintain it in the same direction through the pump regardless of the direction of pump drive.
Another important feature of the present pump resides in the further use of the single vane to relieve excessive pressure in the pumping chamber by permitting it to flow directly from the outlet to the inlet.
The pump of the present invention is also relatively simple in construction and assembly, having very few parts, and is therefore relatively inexpensive.